It is usually thought that Bertha was the daughter of Charibert I, King of the Frankish kingdom centred on Paris, and his wife Ingoberga. Gregory, Bishop of Tours, knew Ingoberga personally and wrote about her in his History of the Franks in the years around 590. Charibert had a complicated marital life and seems to have set Ingoberga aside soon after he became king in 561. However, as Bertha was recognised as legitimate, if she was his daughter, this suggests she could have been born perhaps no later than about 562. According to Gregory, Ingoberga was then about 43 years of age, which means it is possible she was Bertha’s mother, but this was quite late to be having children and would have been unusual at the time. Although it would be easier to explain Charibert and Ingoberga as her parents if Bertha was born somewhat before 562, her subsequent life story indicates it is unlikely she was born much if at all before this date.
Nothing is known of Bertha’s early life, and the tradition that she grew up around Tours seems to be based on her apparent adherence to the cult of St Martin of Tours, to whom the church she later used in Canterbury was dedicated. It is also the case that Ingoberga retired to Tours after she separated from Charibert, which might suggest some connection to the area. However, it may be significant that while Gregory mentions in his History that Ingoberga’s daughter married ‘the son of a King of Kent’, he does not name her. It is the English historian Bede, writing some 150 years later, who introduces the name Bertha and says that she was of the Frankish royal family and was married to the Kentish King Æthelberht.
There has been much debate about when Æthelberht became King of Kent, but scholarly opinion now tends towards this being in around 589 or 590. It seems improbable that the diplomatic match of a marriage to Princess Bertha would have been acceptable in Kent had she been much older than 18 or 20 at the time. If she was born around 562, this suggests the marriage may have taken place around 580. Bede says that under the marriage agreement, Bertha was allowed to practise her Christian faith, although Kent was still pagan at this time, and also that she could bring with her a priest, Bishop Liudhard.
The fact that a Frankish princess married the future King of Kent suggests that the Kingdom of Kent was open to Frankish political influence and that the relationship with Kent was important to Frankia, the most important state in Western Europe at that time. This gave Bertha a role in the international power politics of the time, and it seems credible that this was intended to include paving the way for Æthelberht’s conversion. For the Kings of Frankia, it was beneficial to have friendly Christian monarchs on their north west border. That Bertha was ultimately successful in encouraging Æthelberht to take the step to conversion is indicated by what happened in the final years of the 6th Century. Surviving papal correspondence indicates that Æthelberht invited Pope Gregory to send a Christian mission.
The mission that arrived in Kent in 597 was led by Augustine, Prior at the monastery in Rome that Pope Gregory had founded in his own ancestral home. Augustine soon established the mission in Canterbury, selected by Pope Gregory because he saw the mission as re-Romanising Britain and he believed this was best achieved using the urban infrastructure created by the Romans during their occupation. In Continental Europe, the Church was governed by Bishops based in the towns that still survived from the Roman period. Gregory wanted the same approach in Britain but seems not to have known that the towns in Roman Britain were largely abandoned over 200 years previously as Roman rule fell apart. In 597 they were still mostly empty of people. Nevertheless, Augustine followed his instructions to organise the church in the old Roman towns. There was plenty of vacant land for Æthelberht to make available to Augustine, and the first cathedral in Canterbury was founded where the current cathedral still stands.
It is recorded by Bede that Bertha worshipped at what had been a Roman church, dedicated to St Martin of Tours. It is hard to escape the conclusion that this was the church of St Martin that still stands in Canterbury, which certainly contains much Roman brick in its fabric. However, we currently do not know whether this was a Roman building that Bertha took over, as Bede suggests, or whether it was built for Bertha using recycled Roman brick. There would have been plenty available in the derelict buildings of Roman Canterbury at the end of the 6th Century, and Bertha would have had ready access in Francia to the masons she needed to build in masonry. The link of this church with Bertha was dramatically reinforced in the early 19th Century when a gold pendant, probably from the late 6th Century, depicting the head and name of Bishop Liudhard, was discovered. This was part of a collection that probably formed a necklace in a grave in the churchyard of St Martin’s. It is thought this may have been created for Bishop Liudhard to give to a high-ranking Christian convert.